Traditionally, disposable engine air cleaners perform primarily the function of preventing dirt and other particles from entering the engine air intake. Usually, an air cleaner is attached to an engine intake tube and air enters the cleaner where it passes through a porous media filter before entering the engine intake tube. An example of such an air cleaner is the disposable air cleaner shown and described in the Alseth et al. U.S. Pat. No. 4,350,509, issued Sep. 21, 1982.
Three problems can arise from the use of current air cleaners. In some cases, to reduce cost, a pleated porous media filter is used without an internal support. Because non-woven, porous media filters are subject to collapse if not fully supported, media particles can enter the engine intake if the media does collapse. Second, some engines require a specific amount of negative pressure to assure adequate crankcase ventilation. Current cleaners are not designed to provide a specific level of negative pressure. Third, some engine noise can travel from the intake, back through the cleaner, without being properly attenuated.